“The refusal to offer a place at JFS to M was on the ground that he is not Jewish as a matter of religion. JFS applies the criteria stated by the Chief Rabbi, who is not concerned with whether a child is Jewish as a matter of race, or ethnic origin, but is concerned with religious status.”

Nine of the leading judges in England and Wales this week grappled with the fraught question of who is a Jew as the legal dispute over entry to JFS finally reached the highest secular court, the new Supreme Court.

A three-day hearing before a packed courtroom opened on Tuesday with far-reaching implications not only for other Jewish schools but potentially for those of some other faiths as well.

Britain's leading Jewish school has told the Supreme Court that it had discriminated against a boy of 12 on religious rather than racial grounds when it denied him a place.

A crowded court heard Lord Pannick QC, claim that the boy was refused because the chief rabbi deemed his mother's conversion to Judaism invalid.

JFS had double the number of applicants to places, so children whose mothers were recognised as Jewish were given priority. The boy, known as M, was refused entry because he did not fall into this category, said Lord Pannick, who is representing JFS.

In its first ever judgment, Britain’s new Supreme Court has said that legal aid must continue to be available in the dispute over entry to JFS.

Until now, the Legal Services Commission has funded the father of the boy whose rejection by the school two years ago prompted the legal action.

But the LSC did not want to be liable for paying the costs of JFS and its foundation body, the United Synagogue, in the event that the father lost when the case comes to the Supreme Court later this month.

Jewish primary school heads have voiced dismay that their pupils are not been given priority at JFS.

Vivienne Orloff, head of the Michael Sobell Sinai School, a United Synagogue primary which lies next door to JFS in Kenton, said it was “ridiculous” that children from Jewish primaries did not get preference. “It’s heartbreaking when you have the school on your doorstep. We want all our children to continue their education and what’s important is that the parents want them to.”

JFS has accepted the child of a non-Orthodox-converted mother as a first-year pupil, despite its previous rejection of such children because they are not considered Jewish by the Chief Rabbi.

The Orthodox school, based in Kenton, north London, refused to admit any U-turn or say whether the decision had been taken because of a Court of Appeal ruling earlier this summer declaring its entry policy to be unlawful.

Russell Kett, chairman of JFS governors, said: “The school does not comment on individual applicants or students.”

New rules published this week by JFS in Kenton, North London — and likely to be followed by other Jewish secondaries — will offer places on the basis of points scored for synagogue attendance and other observance.

Parents will also need a certificate signed by their rabbi or another community official to testify to religious practice — mirroring the procedure in some Catholic schools.